Evaluation of the Effect of Adipokinetic Hormone/Corazonin-Related Peptide (ACP) on Ovarian Development in the Mud Crab, Scylla paramamosain

In this study, we identified <i>Sp-ACP</i> and its putative receptor from the mud crab <i>S. paramamosain</i> and explored its potential role in ovarian development. RT-PCR results suggested <i>Sp-ACP</i> was extensively expressed in nervous tissues, the ovary, the middle gut, and the Y-organ, while <i>Sp-ACPR</i> was highly expressed in the ovary. The expression level of <i>Sp-ACP</i> in the ovary, eyestalk, and cerebral ganglia gradually increased during ovarian development, whereas its receptor exhibited an opposite expression pattern in the ovary. Immunofluorescence revealed that ACP was specifically localized in the follicle cells of the ovary. In vitro experiments showed that the expression of vitellogenin receptor (<i>Sp-VgR</i>) in the ovary was significantly increased by 4 and 6 h incubation of <i>Sp</i>-ACP (10 nM). In addition, 12 h injection of <i>Sp</i>-ACP significantly induced the levels of <i>Sp-Vg</i> in the hepatopancreas and <i>Sp-VgR</i> in the ovary, and hemolymph 17β-estradiol titer. Finally, it demonstrated that prolonged injection of <i>Sp</i>-ACP significantly increased the level of <i>Vg</i> and <i>VgR</i> expression, hemolymph 17β-estradiol titer, GSI, and the oocyte diameter. In conclusion, our results suggested that ACP is involved in the regulation of ovarian development of <i>S. paramamosain</i>, likely by inducing hepatopancreas <i>Sp-Vg</i> expression through estradiol and promoting the uptake of <i>Vg</i> by oocytes.